On some features of the shape effect in human dentin under compression

• The inorganic phase of human dentin rules by the shape effect under compression.
• The organic phase decreases the Young's modulus and the compression strength.
• Plasticity of the dentin is increased due to the organic phase.
• Plasticity can be additionally provided by its porosity at d/h ratio ≥ 1.5.

Contribution of inorganic and organic phases of human dentin in the shape effect under uniaxial compression is discussed. Comparison of the deformation behavior under compression of the samples with the different ratios between the diagonal of the compression surface and the height of quartz glass, aluminum oxide and PMMA with dentin samples having similar aspect ratios is carried out. In addition, the comparison of the deformation behavior of these materials under tensile stress is carried out. It has been shown that the shape effect of human dentin under compression is caused by the inorganic phase. The organic phase of dentin is responsible for the lowering of the Young's modulus and the compression strength and the increasing of its plasticity. Plasticity of the dentin can be additionally provided by its porosity, when the d/h ratio of the samples exceeds 1.5.